JACK : connecting a world of audio:
"JACK is system for handling real-time, low latency audio (and MIDI). It runs on GNU/Linux, Solaris, FreeBSD, OS X and Windows (and can be ported to other POSIX-conformant platforms). It can connect a number of different applications to an audio device, as well as allowing them to share audio between themselves. Its clients can run in their own processes (ie. as normal applications), or can they can run within the JACK server (ie. as a 'plugin'). JACK also has support for distributing audio processing across a network, both fast & reliable LANs as well as slower, less reliable WANs."
List of applications supporting JACK.
QjackCtl - JACK Audio Connection Kit - Qt GUI.
The Jack Rack project.
JAMin - JACK audio mastering.
Also, a couple digital audio tools that work with JACK:
ReZound graphical audio file editor.
Ardour digital audio workstation.
Note to self: check 'em out.